Output Interface: States what will the object being studied do to the outside world. The
information here helps build what the states will be in the state chart. In our example, the HallLight is the single output this object deals with. We can think how many states could the HallLight be in. Intuitively, the Hall Light can be turned on and off, so the state in our future state chart will probably have two states: On and Off. Let’s wait to see whether something else needs to be added.